Abstract:
The poly (dimethylaminoethyl methacrylate-
co-hydroxyethyl methacrylate-
co-dodecyl methacrylate, DMAEMA-
co-HEMA-
co-DMA) was synthesized by free radical polymerization. Then stainless steel meshes with different apertures were coated with the polymer or polymer/SiO
2 through impregnation, leading to the pH-responsive oil-water-separation film. The topological structure and wettability of the meshes were analyzed by scanning electron microscope(SEM) and contact angle(CA) test, respectively. The distribution of elements was characterized by X-ray photoelectron spectroscopy(XPS). Furthermore, the oil/water separation capacity of the meshes was tested. The results demonstrated that the surfaces of the meshes turned to be smoother after the coating with the polymers, while they became very rough in case SiO
2 was added into the coating. Besides, the surface wettability varied with pH, which was consistent with the XPS results. Under acidic condition, the coated surfaces were hydrophilic. However, as the media was neutral/slightly alkaline, the surface became hydrophobic. Such change was related to the binding states of nitrogen. The −N− in PDMAEMA was protonated under acidic condition so that the chain stretched and the hydrophilicity was increased. Furthermore, the addition of SiO
2 made the mesh superhydrophilic under acidic condition and superhydrophobic under neutral/slightly alkaline condition, which could be ascribed to the enhancement of surface roughness. When the media was highly alkaline, the wettability of the surface was very unstable due to the chemical reaction of SiO
2 under this condition. Oil/water separation experiments showed that the presence of SiO
2 and polymer enabled the meshes with good capacity for the effective separation of oil and water, and additionally endowed the meshes with a good stability. Meanwhile, when the mass fraction of SiO
2 was 3%, the results collected from infrared oil measurment showed that the meshes presented good separation capacity for oil-in-water emulsion, and the efficiency was more than 99%. Such results were further confirmed by DLS tests.